Upload email recipients without constituent IDs

For school administrators using GiveCampus Outreach. Controls can differ between the classic email editor and the newer Composer editor.

For a direct email recipient CSV, keep the required headers external_id, first_name, last_name, and email_address. The import can accept a row with a blank external ID; it requires an email value to process an email row. Do not guess IDs just to fill the column. Blank IDs can limit constituent matching and data-driven personalization, so preview recipients and merge tokens before sending. A required column header is not the same as requiring an ID in every row. Exclusion uploads and segment/CRM imports have their own schemas.